Aircraft fluid level gauging systems such as, for example, fuel tank level gauging systems, are transitioning from sensors embodied as capacitance-based probes to optically-based sensors. Use of optically-based sensors is advantageous, for example, in that they can reduce or eliminate electrically conductive materials in the fuel tank and therefore are safer than non-optically-based systems. Further, since no electrical wiring is needed inside the fuel tank optically-based sensors act as inherently intrinsically safe sensors.
While optically-based sensors reduce or eliminate electrically conductive materials in the fuel tank (and thus the electrical power transmitted by such materials), there is the potential for excessive optical power being injected into the fuel tank. To address this issue, optical switches are utilized that limit the transmission of optical power into the fuel tank.